Various types of drill chuck assemblies are well known in the art. Typical drill chuck assemblies include a series of clamping jaws for selectively gripping a tool bit. As the clamping jaws advance along the drive spindle axis, the jaw gripping portions of the clamping jaws are advanced radially inwardly, causing the jaw gripping portions to approach each other. When a tool bit is located in the chuck, this radially inward advancement causes the jaw gripping surfaces of the jaw gripping portion of the clamping jaws to eventually contact and fixedly engage the tool bit. When the tool bit is initially inserted into the drill chuck, the tool bit is free to fall to the bottom of the chuck cavity. While this may cause no issues for larger tool bits, it does create some problems for smaller tool bits.
The larger tool bits typically have a larger diameter and a longer gripping shaft. This combination results in a larger tool bit placed in a chuck to pass to the bottom of the chuck and still have the full drilling portion of the shaft of the tool bit exposed. The larger diameter requires less axial advancement of the clamping jaws to secure the tool bit. This combined with the already longer gripping portion of the tool bit shaft allows for easy installation of the tool bit.
The smaller tool bits are typically smaller in diameter and have a shorter gripping shaft. This results in a potential problem if the smaller tool bit is fully inserted into the chuck. This problem results because the gripping portion of the tool bit shaft is shorter than that of the larger tool bits, while the gripping surfaces of the jaws have moved axially forward while closing on the smaller bit diameter, resulting in a shorter gripping portion retained in a longer cavity. Placing a smaller tool bit in a chuck all the way to the bottom often results in a significant portion of the drilling portion of the shaft being contained within the cavity and/or overlapped by the jaws.
In order to prevent this from occurring, the tool bit would need to be held at the desired installation location while simultaneously tightening the chuck to engage the bit. This can be very problematic when attempting to install the tool bit by oneself.